Effect of coronary artery reperfusion on infarct size in swine

The role of ADAMTS13 in acute myocardial infarction: cause or consequence?

Aims

ADAMTS13, a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13, is a metalloprotease that cleaves von Willebrand factor (VWF). There is considerable evidence that VWF levels increase and ADAMTS13 levels decrease in ST-elevation myocardial infarction (STEMI) patients. It is unclear whether this contributes to no reflow, infarct size, and intramyocardial haemorrhage (IMH). We aimed to determine the role of ADAMTS13 in STEMI patients and to investigate the benefits of recombinant ADAMTS13 (rADAMTS13) in a porcine model of myocardial ischaemia-reperfusion.

Methods and results

In 49 consecutive percutaneous coronary intervention (PCI)-treated STEMI patients, blood samples were collected directly after through 7 days following PCI. Cardiac magnetic resonance was performed 4–6 days after PCI to determine infarct size and IMH. In 23 Yorkshire swine, the circumflex coronary artery was occluded for 75 min. rADAMTS13 or vehicle was administered intracoronary following reperfusion. Myocardial injury and infarct characteristics were assessed using cardiac enzymes, ECG, and histopathology. In patients with IMH, VWF activity and VWF antigen were significantly elevated directly after PCI and for all subsequent measurements, and ADAMTS13 activity significantly decreased at 4 and 7 days following PCI, in comparison with patients without IMH. VWF activity and ADAMTS13 activity were not related to infarct size. In rADAMTS13-treated animals, no differences in infarct size, IMH, or formation of microthrombi were witnessed compared with controls.

Conclusions

No correlation was found between VWF/ADAMTS13 and infarct size in patients. However, patients suffering from IMH had significantly higher VWF activity and lower ADAMTS13 activity. Intracoronary administration of rADAMTS13 did not decrease infarct size or IMH in a porcine model of myocardial ischaemia-reperfusion. These data dispute the imbalance in ADAMTS13 and VWF as the cause of no reflow.

Ligating LAD with its whole length rather than diagonal branches as coordinates is more advisable in establishing stable myocardial infarction model of swine

A reproducible and reliable myocardial infarction (MI) model with less inter-individual variation in ischemic size and ventricular function is essential in cardiovascular research. Little is known about whether the different ligation coordinates [whole length of left anterior descending artery (LAD) or diagonal branches] affect the inter-individual variation of ventricular function in the MI model. The present study compared the characteristics of the experimental swine MI model induced by surgical occlusion of LAD in two groups: group A (n=24), where ligation was performed below the second ventricular branch (D(2) branch), and group B (n=23), where ligation was performed at a distance one-third distal to the apex. Variation of ischemic size and left ventricular ejection fraction (LVEF) at 4 weeks after MI was compared between the two groups using the homoscedasticity F test and coefficient of variance (CV). Difficulty in identifying ventricular branches and the great variation of branching patterns encumbered the precise ligation of LAD in group A. The ischemic size and LVEF in group B were less variable than those of group A. There were significant correlations between the percentile of LAD ligation and infarct size or ventricular function. In conclusion, ligating LAD using its whole length rather than ventricular branches as coordinates may be more practical and advisable for establishing reproducible MI models, and this procedure may prove to help standardize the location of occlusion and infarct size.

Combinatorial protein therapy of angiogenic and arteriogenic factors remarkably improves collaterogenesis and cardiac function in pigs

Establishment of functional and stable collaterals in the ischemic myocardium is crucial to restoring cardiac function after myocardial infarction. Here, we show that only dual delivery of a combination of angiogenic and arteriogenic factors to the ischemic myocardium could significantly reestablish stable collateral networks and improve myocardial perfusion and function. A combination of FGF-2 with PDGF-BB, two factors primarily targeting endothelial cells and vascular smooth muscle cells, remarkably promotes myocardial collateral growth and stabilizes the newly formed collateral networks, which significantly restore myocardial perfusion and function. Using various members of the PDGF family together with FGF-2 in an angiogenesis assay, we demonstrate that PDGFR-alpha is mainly involved in angiogenic synergism, whereas PDGFR-beta mediates vessel stability signals. Our findings provide conceptual guidelines for the clinical development of proangiogenic/arteriogenic factors for the treatment of ischemic heart disease.

A new model of myocardial infarction in Yucatan minipigs

Myocardial infarction studies in pigs have been complicated by the use of antiarrhythmic drugs or the high incidence of ventricular fibrillation. We report on a new model of experimental myocardial infarction in thiamylal-anesthetized Yucatan minipigs. These studies were performed in the absence of intravenous antiarrhythmic drugs. No animals required resuscitation during either surgery or reperfusion and only 19% were resuscitated during occlusion. Extensive systemic hemodynamic, regional contractility and coronary blood flow measurements were continuously obtained during left anterior descending coronary artery (LAD) occlusion (45 min) and reperfusion (240 min). Mean arterial blood pressure and left ventricular + dP/dt decreased during occlusion, and both declined further upon reperfusion. Persistent dysfunction (segmental shortening from 24.8 +/- 1.3 to 3.9 +/- 0.9% (p less than 0.001); pre-occlusion and 5 min post-occlusion, respectively) occurred immediately after occlusion in the myocardium perfused by the LAD, while late declines in segmental shortening (19.6 +/- 0.9 to 17.2 +/- 1.2%; pre-occlusion and 240 min post-reperfusion, respectively) were observed in myocardium perfused by the left circumflex coronary artery. While heart rate did not change during occlusion, tachycardia occurred at the onset of reperfusion. Although initial reactive hyperemia following reperfusion was manually inhibited, high LAD blood flow following reperfusion occurred early (0 to 60 min) but returned below pre-occlusion values late (180 to 240 min). The area at risk represented 23.1 +/- 0.9% (n = 34) of the left ventricle and 39.0 +/- 3.2% of this area was infarcted. Therefore, 9.2 +/- 0.9% of the left ventricle was infarcted. These data suggest that myocardical infarction in anesthetized minipigs can be achieved without the aid of intravenous antiarrhythmic drugs and reduced cardioversion. Therefore, this new model can be utilized in the evaluation of therapeutic compounds focused on altering the detrimental consequences of myocardical infarction.